Long memory in temperature reconstructions

Journal of Climate, 2014

A linearized energy-balance model for global temperature is formulated, featuring a scale-invariant long-range memory (LRM) response and stochastic forcing representing the influence on the ocean heat reservoir from atmospheric weather systems. The model is parameterized by an effective response strength, the stochastic forcing strength, and the memory exponent. The instrumental global surface temperature record and the deterministic component of the forcing are used to estimate these parameters by means of the maximum-likelihood method. The residual obtained by subtracting the deterministic solution from the observed record is analyzed as a noise process and shown to be consistent with a long-memory time series model and inconsistent with a short-memory model. By decomposing the forcing record in contributions from solar, volcanic, and anthropogenic activity one can estimate the contribution of each to twentieth-century global warming. The LRM model is applied with a reconstruction...

2018

As presented at the 7th Biennial Conference of the Society for the Study of the Philosophy of Science in Practice in Ghent, Belgium, Summer 2018. See my paper "What is the Thermal Conductivity of Copper?" in the 2021 ASIST Annual Meeting proceedings for citeable versions of these ideas.

2005

The performance of two methods to reconstruct Northern Hemisphere temperature histories of the past millennium is analyzed by applying them to the known development of an extended climate model simulation. The MBH-method underestimates lowfrequency variability significantly, whereas Moberg's method operates satisfactorily. Some caveats apply.

2008

The hedging of weather risks has become extremely relevant in recent years, promoting the diffusion of weather derivative contracts. The pricing of such contracts require the development of appropriate models for the prediction of the underlying weather variables. Within this framework, we present a modification of the double long memory ARFIMA-FIGARCH model introducing time-varying memory coefficients for both mean and variance. The model satisfies the empirical evidence of changing memory observed in average temperature series and provide useful improvements in the forecasting, simulation and pricing issues related to weather derivatives. We present an application related to the forecast and simulation of temperature indices used for pricing of weather options.

Agricultural and Forest Meteorology, 1997

Nonlinear temperature dependence plays a major role in a large variety of ecological models. For the sake of simplicity and efficiency, the temperature dependence functions in many models are calculated for monthly or yearly time intervals, using temperature means or interpolations between means as input. As a consequence, information about the variability of the temperature input data is lost, which leads to a bias in the temperature dependence function and to errors in the model results. We tested the performance of a range of methods against this common approach for calculating temperature dependence on a larger time scale, i.e. for a temporal aggregation. The methods estimate the expected value of the dependence function in different ways, using the mean or standard deviation of temperature variables in different temporal resolutions as input. In our tests we used temperature dependence functions from four different ecological fields; hourly temperature data sets from various climatically differing sites were used as input. The precision of the tested methods increased with the resolution of the input data, although computing time increased. The mean errors ranged from less than 1% to about 8% for the aggregation to 1 month and from about 1% to over 30% for the aggregation to 10 years. The most precise and efficient method is the explicit calculation of the expected value for the dependence function, which is based on the mean and standard deviation of hourly temperatures. The least precise but most efficient method is the common application of the dependence function to mean values. The quality of these methods is mainly determined by the quality of the approximation of the temperature variability. Condensing highly resolved input data into means is only appropriate if either the dependence functions are linear in the observed temperature range, or low precision but very high computing effkiency is required. Given a certain requirement on precision or computing effkiency, we are now able to indicate for a number of input data resolutions the appropriate method to calculate temperature dependence over long time periods. 0 1997 Elsevier Science B.V.

Climatic Change, 2021

The article offers an overview of the time frames used in instrumental series and how to transform them into modern units. In the early instrumental period, time was measured with sundials or mechanical clocks regulated every day with the culmination at noon, making reference to the apparent solar time (AST) and the local meridian. Every day had a slightly different duration, start, and end for the apparent changes of speed of the Sun. When canonical hours were used, hours were computed starting from twilight. In the late eighteenth century, the start was established at midnight. In the mid-nineteenth century, when precise clocks were available, it was possible to adopt an average time, with all days having the same duration, but related to the local meridian. A further step was to unify the time of all cities of a country adopting the time of the capital. Finally, the interregional rails, the telegraph, the telephone, and the international contacts required to unify the different time frames. This lead to the creation of the Coordinated Universal Time (UTC) and the time zones (TZ). The change from AST to UTC introduced two important time differences: one related to the variability of the apparent solar motion and one related to the longitude of the site. Instrumental records, especially the longest ones, are affected by changes in time frames that may cause bias. In this paper, the time changes of 92 selected European cities when they passed from AST to Western European Time, Central Europe Time, or Eastern Europe Time, are considered, and the departures during the calendar year are calculated. Moreover, the bias in temperature derived from the time frame change has also been evaluated in ten case studies over Europe. This paper will assist historians and climatologists to recognize and correct the time departures that affect meteorological series concerning temperature, barometric pressure, and other variables with daily cycles. This correction is crucial to assess climate changes. Specific aims are as follows: to make a friendly explanation of the methodology to pass from old time frames to UTC; to provide transformation equations to remove the bias for the time difference; to pass from time difference to temperature bias to homogenize early records with modern ones.

Geosphere

Advances in low-temperature thermochronology, and the wide range of geologic problems that it is used to investigate, have prompted the routine use of thermal history (time-temperature, tT) models to quantitatively explore and evaluate rock cooling ages. As a result, studies that investigate topics ranging from Proterozoic tectonics to Pleistocene erosion now commonly require a substantial numerical modeling effort that combines the empirical understanding of chronometer thermochemical behavior (kinetics) with independent knowledge or hypotheses about a study area's geologic history (geologic constraints). Although relatively user-friendly programs, such as HeFTy and QTQt, are available to facilitate thermal history modeling, there is a critical need to provide the geoscience community with more accessible entry points for using these tools. This contribution addresses this need by offering an explicit discussion of modeling strategies in the program HeFTy. Using both synthetic ...

Climatic Change, 2013

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1996

The System Ecology Reports consist of preprints and technical reports. Preprints are articles, which have been submitted to scientific journals and are hereby made available to interested readers before actual publication. The technical reports allow for an exhaustive documentation of important research and development results. Die Berichte der Systemökologie sind entweder Vorabdrucke oder technische Berichte. Die Vorabdrucke sind Artikel, welche bei einer wissenschaftlichen Zeitschrift zur Publikation eingereicht worden sind; zu einem möglichst frühen Zeitpunkt sollen damit diese Arbeiten interessierten LeserInnen besser zugänglich gemacht werden. Die technischen Berichte dokumentieren erschöpfend Forschungs-und Entwicklungsresultate von allgemeinem Interesse.

Journal of Climate, 2021

Heat waves such as the one in Europe 2003 have severe consequences for the economy, society, and ecosystems. It is unclear whether temperatures could have exceeded these anomalies even without further climate change. Developing storylines and quantifying highest possible temperature levels is challenging given the lack of long homogeneous time series and methodological framework to assess them. Here, we address this challenge by analysing summer temperatures in a nearly 5000-year pre-industrial climate model simulation, performed with the Community Earth System Model CESM1. To assess how anomalous temperatures could get, we compare storylines, generated by three different methods: (1) a return-level estimate, deduced from a generalized extreme value distribution, (2) a regression model, based on dynamic and thermodynamic heat wave drivers, and (3) a novel ensemble boosting method, generating large samples of re-initialized extreme heat waves in the long climate simulation.All method...